The Science of Interstellar

Image Credit: Interstellar (2014)

Eniola Kasim examines the movie Interstellar and some of the scientific concepts behind the movie.

Interstellar was a 2014 science-fiction epic directed by Christopher Nolan and starring Matthew McConaughey, Anne Hathaway as well as a long list of Hollywood A-listers. Grossing over $677.5 million at the box office worldwide “Interstellar” was a commercial success. The film is set in a dystopian future where the earth is slowly becoming uninhabitable and humanity is on the brink of extinction. The story follows a team of NASA scientists, engineers and pilots who travel through a wormhole in space in a last-ditch attempt to find a new planet that could sustain human life.

While the plot might have seemed grandiose and like speculative science-fiction, some of the main concepts of this movie are rooted in theoretical physics. One of the most striking things about Interstellar is how visually intriguing the artist made space look. And, in the year of the movie’s release it won the Academy Award for Best Visual Effects, and rightfully so. This is because many of the films stunning visuals were created using real world science. The premise for interstellar was developed by producer Lynda Obst and American theoretical physicist Kip Thorne, an expert on blackholes and wormholes who provided the math that the special effects artists used to create the movies spectacular visuals. From the appearance of the blackhole to the mechanism by which the wormhole in the movie worked, real world physics is used to bring these concepts to life.

In the film, the spaceship Endurance and its crew must travel to the distant corner of the universe in order to find a new planet for humanity to live on. However, the only way to get to a distant corner of the universe is to find a blackhole and travel through its wormhole.

Blackholes are a phenomenon predicted by Albert Einstein’s Theory of General Relativity. A blackhole is a region of space in which the gravitational field is so powerful that nothing, including electromagnetic radiation such as visible light, can escape its pull – it is like a bottomless pit in space-time. Current theory suggests that as an object gets sucked into or falls into a blackhole, it approaches a point within the centre of the blackhole called a singularity. A singularity is a one-dimensional point at the centre of a blackhole which contains a huge mass within an infinitely small space. At this point, density and gravity become infinite and space-time curves infinitely, and the laws of physics as we know them cease to operate. As the physicist Kip Thorne describes it, a singularity is "the point where all laws of physics break down." Objects approaching the singularity pass through an event horizon which acts like, a one-way membrane, from which they can never return. If two singularities in far-apart locations could be merged, a wormhole tunnel could be formed.

Like blackholes, wormholes were also predicted by Einstein’s theory of General Relativity. Wormholes or Einstein-Rosen bridges are a hypothetical 'bridge', formed by space-time bending to bring two distant points in the universe closer together to create a shortcut for long journeys across the universe. They consist of two mouths, with a throat connecting the two. In two-dimensional diagrams, the wormhole mouth is shown as a circle. Seen in person, a wormhole would be a sphere. A gravitationally distorted view of space on the other side would be seen on the sphere's surface. If the purpose of a blackhole is to act like a vacuum and suck things into it – a wormhole functions to deliver that matter into a different space-time. The film offers a nice simple explanation of this phenomena – there are two points on a piece of paper; drawing a line between these two points shows the distance between these points in normal space time. If you were to fold this paper almost twice over and poke through the paper with a pencil to connect those two dots, you would create a shortcut through space time much like a wormhole.

In the movie, the crew travels to Gargantua, which is a fictional supermassive blackhole near Saturn with a mass 100 million times that of the sun. This particular blackhole rotates at 99.8 percent of the speed of light or approximately 299.193 kilometres per second (the speed of light in a vacuum is about 299,792 kilometres per second) which is staggeringly fast in comparison to the rotation speed of the surface of earth at the equator, which moves at rotates 0.46 kilometres per second. Gargantua is depicted as a disk-shaped blackhole outlined by a halo of light.

This light enveloping Gargantua is due the blackhole being surrounded by an “accretion disc” containing gas and dust with the temperature of the surface of the sun. This disc provides light and heat to Gargantua's planets. Accretion disk refers to a disk-like flow of particles around an astronomical object, such a blackhole, in which the material orbiting in the gravitational field of the astronomical object possess enough rotational or angular momentum that it does not fall inward toward the astronomical mass along a straight line. Instead it follows a disk like path losing energy and angular momentum as it slowly spirals inward. The blackhole's complex appearance in the film is due to the image of the accretion disc being warped by gravitational lensing into two images: one looping over the blackhole and the other under it. To date, this is the most accurate simulation of what a blackhole would look like and was the product of a year of work by 30 people and thousands of computers.

After passing through the wormhole, which is shown in the film as being 2 kilometres wide and 10 billion light-years long, the crew lands on an ocean planet where time moves much more slowly than on earth. This plot point is another feature of Einstein's theory of relativity which states that time passes slower in higher gravity fields. So on a planet orbiting close to a blackhole, a clock ticks much more slowly than on a spaceship orbiting farther away.

While the movie did a fantastic job of depicting blackholes and wormholes based on real world mathematics and astrophysics, these phenomena have never been observed directly in the real non-cinematic world. However, the general consensus is that these phenomena do exist and some physicists are encouraged to think that real counterparts may eventually be found or fabricated.